Prevalently used conventional filter devices are classified by filtering means into those of a screen type provided with, for example, a metal screen, a perforated panel or a slit panel, those of a cyclone type and those of a centrifugal separation type, and are classified by cleaning system into those of a shaking system, those of a scraping system and those of a backwash system.
The most serious problem in the conventional filter devices is a method of discharging foreign matters deposited on the screen to prevent the clogging of the screen with foreign matters. Although various filter devices of a shaking system, a scraping system and a backwash system have been proposed, those prior art filter devices need a discharge means of a large scale greater than that of their screening devices and require a high manufacturing cost, and the cleaning systems of those prior art filter devices are short of a perfect cleaning means.
It is an object of the present invention to provide a high-performance, economically advantageous filter device of a simple, rational construction, capable of drastically solving technical problems residing in the prior art, easy to design and manufacture, capable of easily removing foreign matters deposited on a screen and discharging the foreign matters removed from the screen by either manual operation or automatic operation using actuators, and capable of being constructed in a large scale without entailing any problem.